Hot wire detonators in existing tactical warhead safe and arm devices explode readily if exposed to high temperatures, shock, static discharges, or electromagnetic interference induced currents. For this reason, military standards require that safe and arm designs have a physical barrier between the detonator and the warhead explosive to provide safety in the event of premature detonator firing. This barrier must be mechanically removed during the warhead arming sequence. Mechanical failure is common, and packaging flexibility within the warhead is limited with the use of mechanical safe and arm devices.
For shaped-charge antiarmor warheads employed in tactical minimissiles such as WASP or the Assualt Breaker terminally guided submissiles, the length required for mechanical safe and arm devices is an appreciable percentage of the total length allocated for ordnance. Also, it is common for such minimissiles to include an infrared or millimeter wave seeker which further requires space within the warhead. Thus, the actual amount of explosives carried by the warhead is unduly limited and the resulting problem is compounded by the fact that the warheads are required to defeat increasingly resistant armored targets.
A partial solution to the problems arising from the use of mechanical safe and arm devices is a safe and arm device which uses a flying plate or slapper detonator. Such flying plate detonators are known in the art and can initiate insensitive secondary explosives such as hexanitrosostilbene (HNS) directly and, therefore, do not require barriers in the explosive train. The length required for such a flying plate detonator is only 0.040 inch (1 millimeter). An (HNS) explosive acceptor pellet is embedded in the warhead explosive to provide a completely inert safe and arm device in a manner that greatly simplifies the assembly, testing, and logistical concerns associated with the warhead.
Flying plate detonators, as known in the art, require a firing current of approximately 1500 amperes for a few microseconds. This characteristic makes the safe and arm device immune to static discharges and electromagnetic interference. Direct connection with a 60 hz, 110 V or 220 V current or with 28 V DC missile battery power will dud the detonator and will not initiate an explosion. The HNS pellet is as insensitive to heat as the LX-14 explosive commonly employed in a warhead. This type of explosive burns rather than detonates if exposed to flame.
The flying plate detonator has not, however, provided a complete solution to the need for a safe and arm device for tactical missiles and warheads. This is because it is necessary to provide a compact and reliable triggering circuit for initiating the detonation of the flying plate detonator. Since there is no mechanical barrier employed within the flying plate detonator, it is extremely important that the triggering circuit not generate transient or spurious signals capable of triggering the detonator.